Plant lectins are used widely as probes of membrane structure. These proteins bind to carbohydrate groups on the cell surface and, in many cases, alter physiological states of the cells. Lectins are used, for example, to distinguish differences between normal and transformed cells. Some lectins stimulate mitogenesis in lymphocytes. As such, these mitogenic lectins are used as immunogen models. Our studies have concentrated on two lectins. One is concanavalin A, a mitogen which is probably most extensively studied and used. The other lectin is obtained from lima bean and we designate this as LBL4 and LBL8 to distinguish a tetrameric and octameric form. Both lectins require metal ions for activity. The research program is directed toward studying the metal ion binding properties of the lectins. Direct metal ion binding studies and indirect spectroscopic assays are being used. Sugar binding to different metallized states of the lectins is being studied. Chemical derivatives of these proteins are being prepared. Their metal ion sugar binding properties are being examined. The general purpose of the research is to explain how lectins interact and modify cell surfaces.